CN103048098B - Oil pipe column connector metal to metal seal face ultrasonic imaging inspection method - Google Patents

Abstract

A kind of oil pipe column connector metal to metal seal face ultrasonic imaging inspection method; Use ultrasonic transducer to launch wide band ultrasound wave to sealing surface, receive the reflection echo signal of sealing surface simultaneously.Based on the propagation law that ultrasound echo signal changes with frequency difference at the reflection coefficient of contact interface, echoed signal is transformed to frequency domain and calculates the centre frequency of amplitude spectrum or high and low frequency band energy ratio, as the indication parameter of sealing surface contact, move ultrasonic transducer along oil pipe axis and circumferencial direction and carry out scanning survey, the distributed image of the contact of sealing surface can be obtained, indicate whether to exist the position of defect and defect, direction, size, ensure the safety of tubing string; Compared with prior art, greatly reduce the processing requirements to coupling surface, improve stability and reliability.

Description

Oil pipe column connector metal to metal seal face ultrasonic imaging inspection method

Technical field

The present invention relates to the Dynamic Non-Destruction Measurement that oil pipe connects airtight quality, the particularly ultrasound inspection methods in metal to metal seal face.

Background technology

Oil pipe uses in a large number in natural petroleum gas field, along with deep-well, horizontal well exploratory development technology are constantly promoted, and the large-scale development of rock gas, require more and more higher to tubing string sealing property.Current oil pipe Special threading connector adopts the metal to metal seal design of innovation, than API modular connection, there is more excellent sealing property, but due to colliding with in the machining tolerance of special thread, transportation, torque wrench moment is unreasonable, oil pipe repeatedly goes up shackle etc., sealing property is very easily caused to lose efficacy, likely cause a serious accident, be therefore necessary to detect tubing string airtight quality.

Current scene adopts helium package seal checker to carry out sealing face leakage detection, in tubing string, helium, nitrogen mixture gas is injected when oil pipe is installed, be forced into setting, detected outward with or without helium leakage at box cupling by highly sensitive helium molecular detector, judge sealing, this method testing cost is higher, and the leakage path existed can only be detected, but cannot detect the small defect on sealing surface, and this little defect is around under environmental activity, develops into new leakage path most probably.Therefore, the existence of these little defects produces potential risks to airtight quality, also must be able to detect.

Special threading connector has higher contact in sealing surface region, and when sealing surface has defect, contact can diminish.Adopt ultrasonic method can measure the contact at interface, sound wave is sent by ultrasonic transducer and incides follow-up the resuming of box cupling through couplant (usually using water) and broadcast, when running into sealing surface, part energy reflects back by receive MUT, and another part acoustic wave energy is through sealing surface.Different contacts, the reflection of sound wave on sealing surface distributes different with transmission potential, and when contact becomes large, sound wave easily penetrates sealing surface, and reflected energy reduces, and transmitted wave energy increases.Can characterize the size of contact with the reflection coefficient of the sound wave ratio of incident wave amplitude (the reflection wave amplitude with), mobile ultrasonic transducer carries out axial and circumferential two-dimensional scan measurement along sealing surface, just can obtain the distribution of contact image on sealing surface.The advantage of ultrasonic method is that equipment cost is low, portable, and can detect micro-defect that may cause leaking.Current existing method (publication number: CN101542277) is by measuring the echo amplitude of the multiple position of oil pipe column connector, and be normalized with the minimum value of measurement result amplitude and maximal value, eliminate the impact on echo amplitude absolute size, but the method requires that the coupling surface of tubing string has consistent surfaceness and situation, and to ensure that the coupling of sound wave in the process measured is consistent.When reality uses, ultrasound wave is easy to the impact by coupling surface roughness (make-up tong dental impression), need before detection to carry out careful grinding process to the surface of box cupling, the impact of coupling effect is also subject in addition in the process of scanning, measurement result is caused to have larger deviation, repeatability is bad, and that is existing method has certain restriction.

Summary of the invention

The object of this invention is to provide a kind of method not relying on reflective sound wave amplitude measurement, to reduce the requirement of effects on surface flatness, obtain testing result comparatively reliably.

The present invention is based upon on the reflection of sound wave when contact interface and transmission regular basis, and research finds: under same frequency, contact is larger, and sound wave reflection is less, transmission is larger; When contact is identical, low-frequency sound wave is less than high frequency sound wave reflection, and transmission is large.So when comprising the sound wave incident contact interface of multiple frequency content, reflection echo medium and low frequency composition is less, and radio-frequency component is more, when contact becomes large, reflection echo medium and low frequency composition and radio-frequency component all tail off, but comparatively speaking low-frequency component loss is larger.

The present invention is based on the propagation law that ultrasound echo signal changes with frequency difference at the reflection coefficient of contact interface, evaluated the airtight quality of oil pipe column connector by the energy distribution that statistics sealing surface reflective sound wave is relative in frequency domain, overcome existing method and be subject to oil pipe rough surface and the restriction of the stable impact that is coupled.The present invention is realized by following technical scheme:

1, select centre frequency between 3-8MHz and-6dB bandwidth be not less than 70% ultrasonic transducer 5, with 0 ° ~ 10 ° orientation to box cupling 3 surface emitting sound wave;

2, ultrasonic transducer 5 used receives the reflection echo signal at sealing surface 2 place simultaneously;

3, use the Hanning window method in digital signal processing to intercept reflection echo W (t), and calculate amplitude spectrum by Fourier transform (formula 1), in formula, t is the time, and f is frequency,

$\stackrel{\‾}{W}\left(f\right)=\left|\frac{1}{2\mathrm{\π}}{\∫}_{-\∞}^{\∞}W\left(t\right)e^{-i2\mathrm{\πft}}\mathrm{dt}\right|---\left(1\right)$

The signal edge of intercepting can be set to 0 by Hanning window method, reduces the discontinuous effect because signal cutout produces, and reduces the distortion that spectrum leakage brings.

4, calculate each frequency-portions relative energy in amplitude spectrum, available centre frequency (formula 2) or the energy ratio of a high frequency band to a low one value (formula 3) represent, f in formula _mfor the crest frequency of amplitude spectrum, f _l∈ [0, f _m], f _h∈ [f _m, ∞];

$f_c=\frac{{\∫}_{f_L}^{f_H}f\stackrel{\‾}{W}\left(f\right)\mathrm{df}}{{\∫}_{f_L}^{f_H}\stackrel{\‾}{W}\left(f\right)\mathrm{df}}---\left(2\right)$

$R=\frac{{\∫}_{f_M}^{f_H}{\stackrel{\‾}{W}}^2\left(f\right)\mathrm{df}}{{\∫}_{f_L}^{f_M}{\stackrel{\‾}{W}}^2\left(f\right)\mathrm{df}}---\left(3\right)$

5, move ultrasonic transducer (5) along oil pipe (1) axial and circumferential and carry out two-dimensional scan, gray level image or pcolor are transferred to the data obtained, or mobile oil pipe (1) completes two-dimensional scan, or move ultrasonic transducer (5) and oil pipe (1) completes two-dimensional scan simultaneously.

Compared with prior art, greatly reduce the processing requirements to coupling surface, improve stability and reliability.

Accompanying drawing explanation

Fig. 1 supersonic detection method schematic diagram

The electric signal that Fig. 2 ultrasonic transducer exports

When the normal contact of Fig. 3 and zero contact, echo amplitude is composed

Fig. 4 is along oil pipe circumference and axial scan imaging results

In figure, 1. oil pipe, 2. sealing surface, 3. box cupling, 4. ultrasound emission receiving instrument, 5. ultrasonic transducer, 6. cavity, 7. clamping device, 8. coupling surface reflection wave, 9. sealing surface reflection wave, 10. coupling surface reflection wave amplitude spectrum, 11. sealing surface reflection wave amplitude spectrums

Embodiment

Detect for one the tubing string sealing surface ultrasonic imaging that diameter is 88.9mm, the present invention is described in further detail.

With reference to figure 1, oil pipe 1 and box cupling 3 are coupled together by screw thread, form metal to metal seal face 2 by the end face of oil pipe 1 and the shoulder of box cupling 3, the inner and outer spaced-apart by oil pipe.When installing, as requested, sealing surface 2 must reach certain contact, and damage can not be had to exist.Focused transducer 5 is fixedly mounted on transducer clamping device 7, and adjustment incident angle is 7 °, is full of the cavity 6 of clamping device 7, and is flowed away by the space between clamping device 7 and box cupling 3 through the water of degasification through water inlet.Glassware for drinking water in clamping device has ultrasonic wave-coupled effect.Ultrasound pulse transmission receiving instrument 4 is used to launch a high-voltage rectangular pulse excitation focused transducer 5, after in water, radiate supersonic wave enters box cupling 3, focus on sealing surface 2, and there is reflection and transmission, the sound wave of reflection returns via former road, is focused ultrasonic transducer 5 and receives and transfer electric signal to and export AD capture card to and transfer digital signal analysis to.

Fig. 2 is a typical Received signal strength, and the signal before 20 μ s does not comprise significant information, is clipped.The signal gathered comprises reflection wave 8 and the sealing surface reflection wave 9 on box cupling 3 surface.The amplitude of roughness on reflection wave 8 and 9 on box cupling 3 surface has impact, so directly assessing sealing surface quality with the amplitude computational reflect coefficient of reflection wave 9 exists uncertain factor.Sound wave is at the reflection and transmission coefficients of two solid material surface of contact except outside the Pass having with the roughness of surface of contact, contact, and also relevant with sound wave frequency, the reflectance ratio high frequency sound wave of low-frequency sound wave is low, more easily penetrates contact interface.Therefore when wide band ultrasound wave incides sealing surface, the low-frequency component comprised in reflection wave is fewer than radio-frequency component, and the loss of contact larger low-frequency component is relatively more.

The amplitude spectrum of sealing surface reflection echo when curve 10 is sealing surface 2 zero pressures in Fig. 3, the amplitude spectrum of reflection wave when curve 11 is sealing surface 2 normal contacts.When the value of the consistent situation lower curve 11 of box cupling 3 surfaceness, coupling condition ought to lower than curve 10, but measured result is just the opposite, this is mainly positioned at box cupling 3 circumferentially diverse location due to twice measurement point, and box cupling 3 surfaceness is not identical.If now by the quality of the height analysis sealing surface of signal, the conclusion of mistake will be obtained: curve 11 measuring position place contact is less than the contact of curve 10 measuring position.

Centre frequency and the energy ratio of a high frequency band to a low one value of amplitude spectrum is calculated, as the characterization parameter of relative contact pressure by formula (2) and formula (3).

A series of defect has been made at the sealing surface circumferencial direction diverse location of oil pipe 1, then install with box cupling 3, mobile clamping device 7, focused transducer 5 accompany movement, along oil pipe axially every 0.1mm, along the circumferential direction carry out one-shot measurement every 1 °, calculate waveform centre frequency f according to the method described above _c, and frequency resultant measurement is along the circumferential direction launched into 360 °, form gray-scale map as shown in Figure 4, horizontal ordinate is circumference 360 °, compressional wave mark distance vertically, unit mm.Bright area correspondence and high center frequency in figure, the corresponding low centre frequency of dark areas, the position that namely contact stress is little is also sealing surface defect location.Discovery is compared, imaging results and made defect one_to_one corresponding with actual fabrication defect location.

Claims (1)

1. a ultrasound inspection methods for oil pipe column connector metal to metal seal quality, is characterized in that:

(1) select centre frequency between 3-8MHz and-6dB bandwidth be not less than 70% ultrasonic transducer, launch sound wave with 0 ° ~ 10 ° orientation to coupling surface;

(2) ultrasonic transducer receives the reflection echo signal at sealing surface place simultaneously;

(3) use the Hanning window method in digital signal processing to intercept reflection echo W (t), and calculate amplitude spectrum by Fourier transform formula (1):

$\stackrel{\‾}{W}\left(f\right)=\left|\frac{1}{2\mathrm{\π}}{\∫}_{-\∞}^{\∞}W\left(t\right)e^{-i2\mathrm{\πft}}\mathrm{dt}\right|---\left(1\right)$

In formula, t is the time, and f is frequency,

(4) calculate each frequency-portions relative energy in amplitude spectrum, represent with centre frequency formula (2) or the energy ratio of a high frequency band to a low one value formula (3),

$f_c=\frac{{\∫}_{f_L}^{f_H}f\stackrel{\‾}{W}\left(f\right)\mathrm{df}}{{\∫}_{f_L}^{f_H}\stackrel{\‾}{W}\left(f\right)\mathrm{df}}---\left(2\right)$

$R=\frac{{\∫}_{f_M}^{f_H}{\stackrel{\‾}{W}}^2\left(f\right)\mathrm{df}}{{\∫}_{f_L}^{f_M}{\stackrel{\‾}{W}}^2\left(f\right)\mathrm{df}}---\left(3\right)$

F in formula _mfor the crest frequency of amplitude spectrum, f _l∈ [0, f _m], f _h∈ [f _m, ∞];

(5) move ultrasonic transducer along oil pipe axial and circumferential and carry out two-dimensional scan, transfer gray level image or pcolor to the data obtained, or mobile oil pipe completes two-dimensional scan, or moves ultrasonic transducer and oil pipe completes two-dimensional scan simultaneously.